Those striving to help women put their biological clocks on hold have come up with the next audacious step in high-tech baby making: freeze-dried eggs that could be preserved for years.

In what could be the newest frontier in assisted reproduction, scientists are working on a technique that may one day allow a woman to store her freeze-dried eggs at home and rehydrate them when she’s ready to have a baby.

Once resurrected, the eggs would be fertilized with sperm and any resulting embryo transferred back into the woman.

In one experiment, researchers “powderized” 30 cow eggs, 23 of which were successfully revived, according to a report in New Scientist magazine.

The technique has already been used to freeze dry stem cells and red blood cells. “Now, the next step is eggs,” Amir Arav, the technology’s developer, told Postmedia News in an interview from Tel Aviv, Israel.

Arav, of Core Dynamics, a biotechnology company focused on advanced cell and tissue preservation, says freeze-drying could be a safer alternative to today’s more conventional method of egg freezing, where eggs are flash frozen and then stored in tanks of liquid nitrogen at fertility clinics.

With liquid nitrogen, the eggs can become contaminated or the cells can become damaged if the temperature isn’t perfectly controlled.

Home storage would also be far cheaper and more convenient, Arav said.

The new technique involves using an ultra fast cooling technique called vitrification that allows no time for cell destroying ice crystals to form in the eggs. Instead, the eggs are cooled into a glass-like solid state.

Fertility clinics across Canada are already using vitrification to cryopreserve eggs.

Arav says his approach involves using a small volume of a “secret” solution and rapid cooling using a liquid-nitrogen “slush.”

Next, the vitrified eggs are placed in a low-pressure chamber under low temperature for 24 hours for full drying. The glass water changes from a solid to a gas in a process called desorption. The result: lyophilized, or freeze-dried eggs that could remain in a dry state at room temperature for years, Arav says.

The eggs would need to be stored in vacuum-sealed packs and protected from light, he added.

Arav is working with collaborators from Yale University and the University of Teramo in Italy.

In experiments with cow eggs, fluorescent staining showed the rehydrated eggs were alive, as well as the cluster of nourishing cells called the cumulus oophorus that surround the egg.

“Of course, we need to show that they can be fertilized and produce a normal embryo and a normal pregnancy,” Arav said. “This is just the beginning.”

About one-third of Canada’s fertility clinics are now using vitrification to freeze and bank eggs for fertility preservation, effectively allowing women to put their biological clocks on hold.

In experienced labs, 80 to 90 per cent of eggs survive the freeze-thaw process and, as the technology advances, pregnancy rates are increasing. In October, the American Society for Reproductive Medicine decreed the technique no longer “experimental,” saying that, in young patients, egg freezing has been shown to produce pregnancy rates comparable to IVF cycles using fresh eggs. Still, the U.S. group — whose positions strongly influence practice in Canada — stopped short of endorsing widespread use of egg freezing simply to defer pregnancy. “Social” egg freezing can raise false hopes, because there is no guarantee the eggs would lead to a pregnancy years later once they’re thawed.

Arav says there are many benefits to preserving eggs over embryos when women or couples are looking to postpone parenthood. (Some fertility clinics are also freeze-banking embryos created via in vitro fertilization for future use). For one thing, it avoids potentially messy custody battles over frozen embryos if the relationship falls apart. “It’s much better to preserve the oocytes (eggs),” he said.

Reproductive biologist Dr. Roger Pierson says some “serious testing” needs to be done in animals before experiments with freeze-dried eggs move into humans.

“It’s conceptually interesting, biologically feasible and might be one of the ways that we start to exercise our reproductive options in the future,” says Pierson, a professor in the department of obstetrics, gynecology and reproductive sciences at the University of Saskatchewan.

“But, just because (an egg) stains with a vital dye doesn’t mean that it’s fertilizable and it doesn’t mean that any embryo that may come out of it is able to fully develop.”

The egg and all its internal structures and DNA would have to remain intact once rehydrated, he said. “This isn’t like grinding it into a powder and having some miraculous cellular reassembly,” he said.

“This is an intriguing idea that bears our deep consideration, but there is a lot of work to be done.”